Field of the Invention
The invention relates to a printing unit cylinder of a rotary printing press and to a bent printing form fastenable on a printing form cylinder of a rotary printing press.
Exemplary of the prior art, the published European Patent Document EP 0 445 645 A1 discloses a printing unit cylinder that is provided with an axially parallel, narrow cylinder gap for receiving therein rubber blanket or printing plate ends. A filling piece for bridging the gap orifice is provided so that when two mutually cooperating cylinders roll over such cylinder gaps, the cylinders are prevented from vibrating. The filling piece is supported on or braced against the rubber blanket or the printing plate on both sides of the gap orifice. It is formed of elastic material and has an outer contour by which it projects beyond the cylinder diameter. The filling piece, furthermore, has a resilient extension that extends radially inwardly into the gap, the filling piece remaining in bearing contact with the rubber blanket or the printing plate via the spring force of the resilient extension.
The published European Patent Document EP 0,430,006 A2 discloses a printing unit cylinder for rotary printing presses. A gap web is arranged at the bottom of the cylinder gap and is releasably fastened in the cylinder gap by a fastening device. The gap web is of such height that the gap webs of two cooperating cylinders meet one another. The gap web is formed as a plate and is subdivided into individual zones by slots extending in the longitudinal direction thereof. Longitudinal slots are assigned to the zones and, when two gap webs meet one another, make it possible for the outer contour of the gap web to spring back elastically.
The published European Patent Document EP 0,697,286 A1 relates to a flexible plate with bent ends for fastening the plate on a cylinder of a rotary printing press. The bent ends are provided, respectively, with fastening tabs arranged in a comblike manner, clearances being provided alternately between the fastening tabs. Starting at one end of the plate from a flexural line of the fastening tabs, the latter extend into the plate. At a second end of the plate, between the fastening tabs, tongues are provided which continue beyond the flexural line of the fastening tabs, the tongues and indentations being adjusted or matched to one another so that, in the fastened state, the tongues and indentations are arranged so as to intermesh like teeth. The tongues are at least of such length that they at least cover the axial opening of the breadth of an outer surface of the cylinder. An aperture angle of the fastening tabs at the print end and an aperture angle of the fastening tabs at the start of printing are formed as supplementary angles.
The published European Patent Document EP 0,699,531 A1 relates to a device for fastening flexible plates with bent ends on a cylinder of a rotary printing press.
In this configuration, fastening tabs arranged in a comblike manner are provided at the bent ends of the printing plates, and the otherwise closed outer surface of the cylinder is provided with a plurality of narrow pockets which are disposed in the axial direction, extending from the outer surface into the interior of the cylinder. The breadth or width of the pockets is greater than the thickness of the printing plates.
The technical problem upon which the solution proposed hereinbelow is based is how to avoid, as much as possible, the excitations of vibrations for printing unit cylinders in printing units of rotary printing presses, in order to achieve higher printing speeds in conjunction with better printing results. Vibrations may lead to a considerable reduction in the press proofing forces prevailing between the mutually cooperating printing unit cylinders, so that the conditions for ink transfer deteriorate quickly, and streaking occurs in the print.
In order to reduce the excitations of vibrations in the printing unit, the method of attaching gap-free rubber blanket sleeves to the rubber blanket cylinder was adopted, such blanket sleeves having become known heretofore from the published European Patent Documents EP 0421 145 A2 and EP 0 514 344 B1. Thus, the disappearance of the gap on the rubber blanket cylinder eliminated the excitation of vibrations by the latter. When planar finite printing plates are used, it is necessary to provide lock-up devices on the plate cylinders in order to fasten the finite printing plates on the circumferential surface thereof. In order to minimize the excitation of vibrations by the lock-up gaps remaining on the printing plate cylinders, the gaps for receiving the lock-up devices were reduced repeatedly further, and the transitions between the mutually opposite ends of the printing form fastened on the circumference of the printing unit cylinder were improved.